The present invention relates to improvements in methods of and apparatus for ascertaining certain characteristics of wrapped or unwrapped tobacco fillers, wrapped or unwrapped fillers of filter material for tobacco smoke and/or similar fillers, rods, streams or analogous bodies which contain a fibrous material. More particularly, the invention relates to improvements in methods of and in apparatus for measuring the density of successive or selected increments of a moving elongated body of fibrous material. Still more particularly, the invention relates to improvements in methods of and in apparatus for measuring the density of successive or selected increments of wrapped or unwrapped fillers of tobacco and/or other fibrous material by means of one or more beams of penetrative radiation.
It is already known to measure the density of successive increments of a wrapped filler of tobacco or the like (hereinafter called cigarette rod with the understanding, however, that the same technique can be relied upon for the testing of all kinds of fibrous materials including fillers which are used for the making of plain and filter cigarettes, cigars, cigarillos and/or filter rod sections) by directing one or more beams of penetrative radiation against the rod so that the intensity of radiation which has penetrated through the rod is a function of the density of the corresponding portion of the rod. The intensity and/or other characteristics of such radiation are monitored subsequent to penetration through the rod, and the signals which are generated by the monitoring means are indicative of the density of the corresponding increment or increments of the rod. In many instances, the means for directing one or more beams of penetrative radiation against the rod is designed to traverse successive increments of the rod within the confines of suitable means for guiding the rod, e.g., a cylindrical sleeve. Signals which are generated by the monitoring means can be processed in a number of different ways, for example, to regulate the density if the monitored density deviates from a desired value, to stop the machine if the difference between the monitored density and the desired density exceeds a preselected threshold value and/or to eject those articles which contain defective portions of the rod.
In accordance with an earlier proposal which is disclosed in commonly owned U.S. Pat. No. 4,424,443, radiation which is caused to penetrate through a rod of fibrous material includes beta rays. It was also proposed to employ X-rays (reference may be had to U.S. Pat. No. 3,056,026 and to commonly owned patent application Ser. No. 572,563); however, applicants and their assignee are not aware of any cigarette makers or analogous tobacco processing machines which employ density measuring apparatus operating with X-rays. A serious drawback of all presently known apparatus which measure the density of tobacco fillers or the like with beams of penetrative radiation is that the radiation is radioactive which renders it necessary to undertake numerous and highly expensive precautionary measures so as to prevent contamination of the plant and impairment of the health of attendants.